The invention relates to a device for the gasification of organic or inorganic materials such as bulk waste based on wood or other biomass, or even municipal waste, waste oil, coal, etc., which generates synthesis gas used as fuel for internal combustion engines and combustion turbines, for example those designed to drive electric generators in cogeneration units.
Hitherto known devices for the gasification of organic or predominantly organic materials such as wood waste, wood chips, straw, sludge, and various forms of biomass, including municipal and other wastes, predominantly utilize a gasification process based on combustion, partial combustion, or fluidized bed combustion of material. In these cases the material is filled from a filling hopper into auger conveyors, through which it is moved and is heated directly or indirectly during the passage through the auger conveyors, during which synthesis gas is developed from the ongoing thermochemical reaction. The synthesis gas is then used as a gaseous fuel for internal combustion engines of cogeneration units.
In these known devices, the major problem is maintaining the stability of the gasification process and achieving a standard high quality of the output synthesis gas, particularly in achieving a low tar and nitrogen content. Precise regulation of the combustion process is difficult, and a disadvantage also lies in the high emissions of ash and other pollutants. The output synthesis gas generally contains tars which are formed during the combustion of pre-dried material with a moisture content of up to 15%. Low moisture, which is a prerequisite of effective combustion, has the undesirable consequence of a high tar content which must subsequently be chemically removed by washing in order to achieve a sufficient quality of synthesis gas for its combustion in internal combustion engines.
In patent application JP 2001 28 94 22 A, the device for the gasification of material is described through its combustion. In order to prevent atmospheric air from entering the device and thus reducing the risk of ignition of the material in the hopper, part of the flue gas from the combustion chamber is filtered, cooled, and fed into the sealing mechanism which is positioned before the entry into the combustion chamber. Conversely, the combustion chamber is supplied with oxygen in order to improve the combustion of the unburnt particles. During the combustion of the material, which must have a low input relative moisture, undesirable tars are not formed but neither is a large percentage of nitrogen, so the output synthesis gas is not of a sufficient quality.
In patent EP 186 5045, biomass enters the device from the tray through a supply auger and then passes through two gasification augers. Below them is positioned a combustion auger, from which both gasification augers are heated. Small biomass particles pass through a sieve from the gasification auger into the combustion auger where they are combusted during the supply of preheated combustion air. Larger particles are returned to the gasification process. The developed synthesis gas passes through the entire device back to the beginning, where it is removed. The device according to EP 186 5045 is designed to allow for a reduction of the nitrogen content in the developed synthesis gas. Given that the gasification augers are not hermetically separated from the combustion auger, the disadvantage of the device is that part of the flue gas continuously penetrates into the gasification augers, so the nitrogen content in the exhaust gas cannot achieve the zero or negligible value optimal for achieving a high quality of developed synthesis gas. The tar content in the synthesis gas is also high, since the material passing through the gasification augers cannot have a high relative moisture due to the subsequent combustion.
The task of the invention is to provide a gasification device which would remove the disadvantages of the known devices, allow for the processing of materials with a high relative moisture, and achieve a high quality of developed synthesis gas with a minimum tar and nitrogen content. A further task is to provide a device with lower emissions, with efficient regulation of the gasification process, and with improved stability of the entire system.
This task is solved by creating a device for the production of gaseous fuel from materials of organic and/or inorganic origin according to the present invention.
The device includes a filling chamber which is connected to at least one supply auger conveyor for supplying material from the filling chamber into the gasification reactor. The gasification reactor comprises at least two heated gasification augers arranged in rows above beneath each other for a serpentine flow of the material through the reactor. Gaseous fuel is formed as a synthesis gas from the thermochemical reaction in the gasification augers and is collected at the outlet which is arranged on the lowest gasification auger.
The subject-matter of the invention lies in each horizontal row of gasification augers being formed by a gasification body whose casing has a closed oval cross-section formed by an upper base, a bottom base, and convex side walls each with a circular arc profile, wherein each gasification body contains at least two gasification augers arranged side by side and mutually partially separated by longitudinal partitions that form half-grooves for the individual gasification augers. The gasification bodies are heated by electric heating, wherein at least one electric heating element is arranged parallel to the lower base and/or to the upper base of each gasification body. The filling chamber is hermetically sealed to prevent the access of atmospheric air when the material is being filled. At least one neck leads into the filling chamber for supplying exhaust gases from the combustion of the synthesis gas in the internal combustion engine. The filling chamber is further provided with at least one neck for the removal of exhaust gases from the filling chamber. The device according to the invention allows for the production of synthesis gas with a lower tar content and almost zero nitrogen content, because the electric heater allows for the processing of materials with a higher relative moisture and with perfect regulated heating in the gasification bodies which, together with the elimination of combustion and with gas-tight closure of the filling chamber, results in an improved quality of the output gas used as fuel gas.
In a preferred embodiment of the invention, the filling auger conveyor is arranged above the uppermost gasification body and is fitted with at least one neck for the supply of water or steam, at least one neck for the supply of heat, and at least one neck for the removal of heat. The material fed into the reactor can thus be moisturized prior to its entry into the first gasification body and preheated to improve the parameters of the gasification process.
In another preferred embodiment of the invention, there is a spacer, positioned between the filling auger conveyor and the uppermost placed gasification body, that contains a moisture sensor for the material and an additional or alternative supply of water or steam for adjusting the moisture of the material. According to the measured moisture values, it is thus possible to make final adjustments to the moisture content of the material to the optimum value also in the spacer just before the material enters into the gasification body.
For ideal mixing and moisturizing of the input material, it is preferred that the filling chamber has a conical shape in its lower part, and leading into the filling chamber are the ends of two supply auger conveyors which are separated inside the filling chamber by a wedge-shaped partition. Towards the opposite ends of the filling conveyor auger are connected two spacers that lead to a joint outlet neck with a flange that is connected to the flange of the inlet neck of the uppermost gasification body.
For universal use for various kinds of organic and inorganic materials, it is preferred that the device comprises three gasification bodies arranged in horizontal rows one above the other, wherein inside each gasification body there are arranged, in parallel in a horizontal plane, four gasification augers separated by longitudinal partitions.
In a preferred constructional embodiment of the device according to the invention, the gasification bodies are horizontally separated from each other by vertical supporting partitions, wherein the electrical heaters are removably placed in gaps between the adjacent bodies and between the adjacent supporting partitions and the side partitions on the upper base of each gasification body. This embodiment allows for easier installation, and repair and replacement of the heaters or their parts. The electric heater preferably comprises a set of heating elements in the form of tubes whose axes extend perpendicularly to the axles of the gasification augers. The device is housed in a cabinet with service holes that allow for the exchange of the heating elements without the need to remove the outer casing of the reactor.
In order to uniformly form an airtight seal of the material in the filling chamber, the filling chamber is preferably provided with two oppositely arranged necks for the supply of exhaust gases, wherein these necks are interconnected through distribution piping. The exhaust gases can thus penetrate into the filling chamber uniformly from both sides. The neck for the release of exhaust gas from the filling chamber is arranged above the two supply necks.
Finally, it is advantageous that the front wall of each gasification body is provided with a common connecting flange for connecting the drives to the axles of the gasification augers in the gasification body.
The advantages of the device according to the invention are that it allows for the generation of high-quality synthesis gas with a minimum content of tars and nitrogen from various kinds of organic and inorganic materials which may have a relative moisture content greater than 50%. An advantage is also the even and intense electric heating of moist material in the gasification bodies with common and uniform heating of several gasification augers at the same time. Another advantage is the simple prevention of the inlet of atmospheric air into the gasification process using exhaust gases that are formed as combustion products of synthesis gas, in an internal combustion engine. The device, in comparison to known reactors, is characterized by low emissions, efficient regulation of the gasification process, and improved stability of the entire reactor system associated with the cogeneration unit.